1. Field of the Invention
The present invention relates to an image forming method in which a recording head and a recording material are moved relative to each other by step driving of a stepping motor to perform a vertical scanning, and a horizontal scanning is conducted at each step driving to form an image onto the recording material.
2. Description of the Prior Art
An image forming apparatus is known in which an image is exposed to light onto a heat-developable light-sensitive material (image forming sheet). The heat-developable light-sensitive material is heat-developed and, subsequently, is superimposed upon an image receiving material. The heat-developable light-sensitive material and the image receiving material are pressurized upon each other, whereby an image is transferred to the image receiving material to obtain the image.
The heat-developable light-sensitive material is wound around a recording drum which is rotated at high speed. The heat-developable light-sensitive material is exposed to light by light rays from light-emitting elements which are mounted on a recording head arranged in correspondence with the recording drum. Means for the light-exposure is scanning recording, in which horizontal scanning is performed by rotation of the recording drum, while the recording head is moved axially to the recording drum to conduct vertical scanning. That is, when the horizontal scanning is completed, the recording head is vertically scanned through one step allowing horizontal scanning to be done on a subsequent line. This is repeated whereby it is possible to record the image onto the heat-developable and light-sensitive material. The vertical scanning of the recording head is conducted by a driving force from a stepping motor. Accordingly, the stepping motor is driven through a predetermined number of pulses each time horizontal scanning, corresponding to one line, is completed. It is thereby possible to obtain horizontal scanning lines equal in pitch to each other.
In case where the stepping motor is driven at high speed and is subsequently stabilized, there is a case where no-vibration driving is impossible. Further, residual vibration occurs more or less when stopped, whereby, as shown in FIG. 5, when an image is recorded, that is, vertical scanning is performed immediately after the occurrence of the residual vibration, horizontal scanning lines 102 recorded on a light-sensitive material 100 meander. On the other hand, after stopping the stepping motor, no residual vibration occurs after a lapse of a long period of time. Thus, as shown in FIG. 5, horizontal scanning lines 104 become substantially straight lines.
Here, the timing for starting image recording is immediately after completion of reading the image data corresponding to one line. Accordingly, in case where the image data is sent at high speed, the vertical scanning lines meander. In case where the image data comes late, the image data is horizontally scanned after completion of residual vibration so that the horizontal scanning lines are brought substantially to straight lines. In this manner, a mixture of the meandering horizontal scanning lines 102 and the substantially straight vertical scanning lines 104 exerts a great influence on the image quality making it impossible to obtain high image quality.
In order to solve the above-discussed problem, the start of horizontal scanning should be delayed until residual vibration is completed. However, this considerably increases recording time so that high-speed recording cannot be done. Further, the image should be recorded at equal intervals of time after the image data corresponding to one image has been stored. In this case, however, a frame memory is indispensable or essential so that a number of component parts increases. This leads to an increase in cost.